1. Field of the Invention
This invention relates to a method of printing a glass pane with a decorative coating, which extends at least in a selected zone right up to the peripheral face of the glass pane.
2. Description of the Related Art
Automobile glass panes are frequently provided along one edge or along the entire periphery of the pane with an opaque decorative coating or film, typically as a baking finish. For applying the decorative coating onto the glass surface, screen-printing has proved especially suitable. The printing ink is usually baked on at temperatures of 550.degree. to 600.degree. Celsius or higher during the course of the heat-treatment necessary for bending and/or toughening the glass panes.
The glass panes in the installed condition are now frequently no longer covered by a profiled frame encompassing the pane at the edge or fitting over the edge, but instead the glass panes are visible from the outside right up to their edges. This means that the decorative print at the edge is visible right up to the periphery of the glass pane. Irregularities in the outer boundary of the decorative frame, especially slightly differing distances between the outer boundary of the decorative frame and the edge of the glass pane, can have a very adverse appearance. A considerable interest therefore exists in being able to print the colored coating forming the decorative frame in selected regions or along the entire periphery of the glass pane right up as far as the peripheral edge.
In the usual printing processes, especially in screen printing, it is difficult for various reasons to carry out an exact decorative application accurately right up to the edge of the glass pane. On the one hand, the glass panes as a rule have certain admissible dimensional tolerances, whereas they are all printed using the same printing template. The positioning operations of the glass panes to be printed and of the printing tools are also accompanied by tolerances, which may be additive to the dimensional tolerances of the glass panes. If the part of the screen printing template permeable to the printing ink projects beyond the edge of the glass pane, the printing ink adheres to the lower face of the screen printing template at these locations and the template becomes unusable. To overcome this difficulty, therefore, the application of the color in the screen printing process is usually performed only up to a distance from the edge of the pane which allows for the most unfavorable case. Printing up to the edge of the glass with accuracy of area is, however, not possible in series printing by means of the screen printing process in the state of the art.